Automatic determination of traffic signal preemption using differential GPS

Claims

We claim:

1. A traffic signal preemption system using differential global positioning system (GPS) corrections, for a signalized intersection having a traffic signal controller capable of operation in a normal mode and in a preemption mode upon receiving a signal for preemption, the system comprising:

a traffic signal subsystem, including;

a GPS reference receiver having an antenna installed at a known position, for receiving GPS signals and computing measurement corrections for the GPS signals;

a communication radio for receiving data from an approaching emergency vehicle, and

an intersection computer, containing a model of the intersection and programmed such that corrected vehicle position, speed and direction measurements are used to determine when to send a signal to the traffic controller to switch to preemption mode in such a way as to minimize disruption of normal traffic;

a vehicle subsystem, including;

a GPS receiver for receiving GPS signals, said signals including signals from which the vehicle's position, speed and direction can be determined;

a communication radio for transmitting data to the traffic signal subsystem radio, and

a vehicle computer, for coordinating operation of the vehicle GPS receiver and the vehicle communication radio; and

a differential GPS subsystem portion in communication with the GPS reference receive to receive therefrom the measurement corrections and in communication with the GPS receiver to receive the GPS signals and to compute and to provide to the interaction computer, corrected vehicle position, speed and direction.

2. A traffic signal preemption system as defined in claim 1, wherein;

the traffic signal subsystem has a radio transmitter by which the GPS measurement corrections computed by the intersection computer are transmitted to the vehicle; and

the vehicle computer computes the corrected measurements of the vehicle position, speed and direction for transmission to the traffic signal subsystem.

3. A traffic signal preemption system as defined in claim 1, wherein:

the vehicle communication radio transmits uncorrected vehicle position, speed and direction measurements to the traffic signal subsystem; and

the intersection computer computes corrected vehicle position, speed and direction measurements.

4. A traffic signal preemption system as defamed in claim 1, wherein;

the vehicle communication radio transmits raw GPS measurements to the traffic signal subsystem; and

the intersection computer computes corrected vehicle position, speed and direction measurements.

5. A traffic signal preemption system as defined in claim 1, wherein;

a single GPS reference receiver serves multiple controlled traffic intersections and broadcasts GPS corrections to multiple vehicles in the same vicinity;

the vehicle computer in each vehicle computes the corrected measurements of vehicle position, speed and direction for transmission to the traffic signal subsystem.

6. A traffic signal preemption system as defined in claim 1, wherein:

the vehicle subsystem includes a turn signal indicator, wherein the vehicle communication radio also transmits turn signal and vehicle identification information to the traffic signal subsystem.

7. A traffic signal preemption system as defined in claim 1, and further comprising:

means for identifying selected points for use in a learn mode on each approach route to the intersection; and

means contained in the traffic signal subsystem, for operating in the learn mode, during which each approach route to the intersection is recorded for use in a normal mode of operation.

8. A traffic signal preemption system as defined in claim 1 wherein corrected vehicle position, speed and direction measurements are used to determine when to send a signal to the traffic controller to switch to preemption at an optimum time in such a way as to minimize description of normal traffic.

9. A traffic signal preemption system as defined in claim 8 wherein;

the traffic signal subsystem has a radio transmitter by which the GPS measurement corrections computed by the intersection computer are transmitted to the vehicle; and

the vehicle computer computes the corrected measurememts of the vehicle position, speed and direction for transmission to the traffic signal subsystem.

10. A method of operating a traffic signal preemption system for a signalized intersection having a traffic contoller, comprising the steps of;

receiving global positioning system (GPS) signals at a reference GPS receiver whose location is accurately known;

computing differential GPS corrections to be applied to received GPS signals;

receiving GPS signals at a vehicle GPS receiver said signals including signals from which the vehicle's position, speed and direction can be determined;

transmitting some form of the received vehicle GPS signals to a traffic signal intersection subsystem;

using the differential GPS corrections, computing corrected vehicle position, speed and direction; and

computing from the corrected vehicle position, speed and direction measurements, taken with known intersection approach data, an o